A boost converter is a step-up power converter that may generate an output voltage greater than its input voltage. It is a class of switched-mode power supply (SMPS) that contains semiconductor switches (e.g., diodes and transistors) and one or more energy storage elements (e.g., a capacitor, an inductor, or combinations thereof). Filters made of capacitors may be added to the output of the boost converter to reduce output voltage ripple.
A bridgeless boost converter may lack a full-rectifier bridge in either of the two conduction paths. Instead, a bridgeless boost converter may be implemented by replacing a pair of bridge rectifiers with switches and employing an alternating current (AC) side boost inductor. Thus, the bridgeless boost converter may avoid power loss caused by the bridge rectifier, thereby improving power efficiency.
An early description of a single phase bridgeless boost converter is included in a publication by Martinez et al. entitled “A High-Performance Single Phase Rectifier with Input Power Factor Correction,” which calls the bridgeless boost converter a rectifier with power factor correction (PFC). This publication lays out the advantages of a single phase bridgeless boost converter, including increased efficiency resulting from eliminating two diode drops with their associated power loss from the path of an incoming line current.
Another publication by Lu et al. entitled “Bridgeless PFC Implementation Using one Cycle Control Technique” describes a single phase bridgeless boost converter applied using a then new principle of one cycle control. This publication calls the bridgeless boost converter a bridgeless power factor correction circuit. A pulse width modulation (PWM) controller with one cycle response is discussed therein. This publication discloses ways of sensing an inductor current and voltage, in order to provide inputs to a control processor. An efficiency of 96% was demonstrated, but only at low power levels (e.g., less than 250 watts). This publication also discusses electromagnetic interference (EMI) issues specific to the architecture used therein.
Further, U.S. Pat. No. 7,940,539 by Esmaili et al. describes a bridgeless boost converter, which is referred to therein as a single phase full bridge boost converter, that is suitable for the purpose of regenerative braking in electric cars.
The publications above describe manifestations of similar circuit topologies. However, none of the publications above describes how to make a single phase bridgeless boost converter truly efficient at high power levels (e.g., over 1,000 watts). As light-emitting diodes (LED) lighting applications may sometimes need to operate under high power level, it is desirable to improve power efficiency for such applications.